1. Technical Field
The present invention relates to a power amplifier system, and more particularly, to a power amplifier system capable of stably supplying current a power amplifier.
2. Description of the Related Art
Generally, a power amplifier is used in order to transmit and receive a signal in a wireless communication system such as a mobile communication terminal. Here, the power amplifier indicates a device amplifying a small signal efficient into a large signal having low distortion to supply the amplified signal to a load through an antenna.
As this power amplifier, a complementary metal oxide semiconductor (CMOS) power amplifier designed by a general CMOS process in a Gallium Arsenide (GaAs) process that is a process of manufacturing a special semiconductor is used. Since the CMOS power amplifier as described above may be mass-produced, it has advantages such as a cheap cost and various functions.
Meanwhile, in order to stably control an operation of the power amplifier, a power adjuster has been developed, and a technology for supplying stable power to the power amplifier using the power adjuster has been studied and developed.
A power amplifier system according to the related art using the power adjuster includes a voltage controller providing constant voltage corresponding to reference voltage to a power amplifier, a current controller adjusting driving current according to input control voltage, and a bias controller controlling bias current applied to the power amplifier using the driving voltage and the driving current, and appropriately adjusts the bias current according to the input control voltage to supply stable current to the power amplifier.
However, as the input control voltage increases, the bias current applied to the power amplifier also increases, and when a magnitude of the bias current applied to the power amplifier is out of a predetermined range, the bias controller does not appropriately control the bias current.
In order to solve this problem, a scheme of inputting low control voltage to the power amplifier system has been used. However, a temporal time delay in which large bias current is applied to the power amplifier until the bias controller is normally operated by the low control voltage may be generated.
Therefore, characteristics of the power amplifier are deteriorated.